Intermodal containers are used to transport goods and materials using a variety of transportation means including rail, highway and/or marine shipping. Intermodal containers are manufactured to standard dimensions to allow shippers to stack and load intermodal containers manufactured by different companies in the same loads without concern tier compatibility between the intermodal containers.
One particular type of intermodal transportation system is commonly referred to as a "Container-On-Flat-Car" (COFC) system. In this system, containers are provided that can carry goods on trucks or on rail cars. In addition, the containers are also adaptable for use in marine shipping.
One specification liar intermodal containers manufactured for COFC systems is promulgated by the Mechanical Division of the Association of American Railroads. Its Specification M-930-90. Revised 1990, titled "Closed Van-Type Dry Cargo Containers for Domestic Container-On-Flat-Car (COFC) Service" which is hereby incorporated by reference, recites detailed requirements relating to dimensions of the COFC containers, their load capacities, strength requirements. The document also sets forth testing protocol for determining whether the intermodal containers meet the requirements.
Another intermodal system is commonly referred to as "Trailer-On-Flat-Car" (TOFC) and typically involves containers adapted to be placed on flatbed railway cars. In this system, truck trailers are themselves loaded on the rail cars and then removed close to their destination where they are then hauled the remaining distance over the roads.
As used in connection with the present invention, the term "intermodal container" is meant to include any container designed for transporting large amounts of goods or bulk materials via a variety of transportation modes, including truck, rail and/or marine shipping. The containers further are able to be moved between shipping modes without unloading or loading their contents. Further, the intermodal containers may be open-topped or they may be completely enclosed depending on the nature of the materials to be hauled and the protection desired. As such, the containers of both of the systems, COFC and TOFC are included within this definition, as are other containers used in other intermodal systems.
Intermodal containers are typically manufactured using sheet metal (typically steel or aluminum) attached to a framework of structural members. As a result, they are themselves typically relatively heavy which limits the loads which can be transported by the containers. Furthermore, the metal used to manufacture the intermodal containers typically corrodes easily, reducing the useful life of the containers. In addition, it may not be desirable or allowable to allow some goods or materials to come into contact with the metal, thereby requiring additional packaging of the goods or materials to prevent contact with the metal of the containers.
Furthermore, where bulk materials such as grain, coal, or even waste materials are being transported, the metal lining the containers makes unloading difficult in many situations. For example, in colder climates moisture in the materials may cause them to freeze to the interior of the container, typically requiring hand labor to dislodge the material. In some situations, the entire container may be heated to facilitate unloading and/or pressurized water may be required to completely unload the container All of these actions raise the cost of transporting materials. In addition, the use of water to clean the containers raises containment and contamination issues at the locale where the containers are unloaded.
Friction between the materials and the container can also make unloading difficult, requiring the operator, in some situations, to rapidly accelerate and decelerate the containers in an attempt to jar the materials loose. Such actions add unnecessary stress and wear to the containers as well as the handling equipment, adding the cost to repair any damage and potentially reducing the useful life of the containers and/or handling equipment.